Hearing aid device



Z3, 19 J. B. NELSON ET AL HEARING AID DEVICE Filed Nov. 19, 193'] TORS CZNVEN wm M A TTORNEYS.

Patented Dec. 23, 1941 HEARING AID DEVICE John B. Nelson, Mount Lebanon, and Willard 0. Mason, Pittsburgh, Pa.

Application November 19, 1937; Serial N0. 175,434

2 Claims. (Cl. 179-107) Our present invention relates to that class of device used for restoring or partially restoring the hearing of individuals with impaired hearin and more particularly relates to a hearing aid device which will enable the wearer thereof to obtain improved reception of conversation and speaking while dampening or eliminating extra-" neous or interfering noises.

Hearing aid devices of the general type herein involved have been known for some years and have made it possible for persons with impaired hearing to compensate, at least partially, for such loss in hearing. Developments along the line of I improved hearing aid devices have generally taken the form of supplying more power and greater sensitivity and remarkable strides have been made in this direction. With increasing power and sensitivity, however, a new disadvantage has arisen in connection with hearing aid devices in that these devices are too sensitive to present invention ,to produce a hearing aid device which, without sacrificing desired power and sensitivity, will improve hearing by limiting the intensity or volume of sound transmitted .to the auditor-year canal to a predetermined constant maximum which will not cause discomfort to the wearer thereof, a

Another object of our invention-resides in producing a hearing aid device which dampens or excludes sound waves or tonesbeyond a certain predetermined frequency range, thus permittingsound waves or toneswithin a desired frequency range to be' heard with greater clarity and distinctness.

A further object of our inventioni resides in so modifying that portion of a hearing aid device which is at or adjacent the wearer's ear that sound-waves or tones within the normal or usual conversational or speaking range will be clearly heard while at the same time dampening or eliminating sound waves or noises-having frequencies beyond-such range.

More specifically, our invention provides a tion with the diaphragm construction utilized in that portion of the hearing aid device at or adiacent the wearers ear and this construction is in the form of a double diaphragm with a liquid therebetween.

Other and further objects and advantages will be understood by those skilled in this art or will be apparent or pointed out hereinafter.

In the accompanying drawing:

Figure 1 illustrates in section a device embodying the present invention and also includes diagrammatically the general arrangement of hearing aid device systems;

Fig. 2 is an exploded view partly in side elevation and partly in vertical section showing our invention on an enlarged scale; and

Fig. 3 is a perspective view of the lower portion of Fig. 2.

me numerals designate corresponding parts in the various views of the drawing.

The hearing aid system is made up of a suitable battery ill, a suitable microphone H, a rheostat l2, and a head phone l3. The battery, microphone and rheostat maybe of any known or ap-' proved types such as those now used and per se form no part of the present invention.

Likewise, the mode of operation of these hearing aid devices is well known but for the purposes of convenience will be briefly referred to here. Sound waves or vibrations in the air as they emanate from any source or sources cause a diaphragm' in'the microphone to vibratein re-- sponse thereto. Vibrations or the microphone I diaphragm cause vibrations in physical and/or pressure conditions within the microphone and these changes in condition alter theelectrical resistance of the microphone. The changes in the microphone resistance are in accordance with the vibrations or sound waves set up from the source and cause corresponding changes in battery current flowing through the microphone ,and the head phone coil.- Thus in eflect the microphone acts as a valve, operated'by the some! waves, which controls the battery current. Variations in battery current through the headphone coil cause magnetic attraction of the headphone magnet tor the head phone diaphragm to effect changes which therefore are in accordance with novel construction audfarrangement in connec. i

the changes in vibrations or sound-waves emanating from the. source or sources. A Gamequently, the varying pull on the head phone diaphragm sets up coirespondingvibration's in such diaphragm and thus causes corresponding variations in pressure of the air in the auditory canal of the ear. These air vibrations in the auditory canal correspond to those emanating from the source except that the microphone has reatly amplified the same.

It will readily be understood from the foregoing explanation of the operation of these devices that the greater the power and/or sensitivity of the hearing aid devices the worse the device becomes insofar as extraneous noises are concerned. By extraneous noises we mean those noises which form no part of what the wearer of the device wishes to hear. For example, if the wearer wishes to hear ordinary speaking or conversational tones, the extraneous noises will include such noises as those resulting from traffic, electrical appliances, or those noises arising from various other sources. We have found that most of these extraneous noises are of higher pitch or frequency than conversational or talking tones. The hearing aid devices now known and used amplify the higher pitched noises to an uncomfortable extent and so as in many cases to prevent the wearer of the device from being able to distinguish speech or conversation due to 'the frequency above the speech range will be found many musical notes and tones as well as noises arising from trafiic, electrical equipment and many other types of extraneous noises, particularly those emanating from metallic contacts.

Our invention limits the volume or intensity output to a substantially constant maximum and dampens those frequencies above the speech range to an extent which prevents such from interfering with hearing speech and conversation while not appreciably impairing the efliciency of the hearing aid device as to the receiving of speech and conversational tones." In other words, the sound waves of frequency above 2048 are dampened to a much greater extent than those within th speech range and by comparison the speech range is received much more clearly and distinctly than is possible with present devices. Loud or irritating sounds and noises are cut down to a comfortable value.

The head phone I3 is made up of two main parts l4 and IS. The part I4 is comprised of a casing I6 provided with a core I I with an electrical winding l8 therearound and a magnetic element l9 provided with three cobalt steel magnets 20 spaced at 120 intervals. This portion of the hearing aid device is likewise conventional. Casing i6 is provided with a threaded extension 2!. vention, comprises a cylindrical portion 22 inf ternally threaded at 23 connected to and merging with a second and smaller cylindrical portion 24 also internally threaded as at 25. Portions 22 and 24 are connected by the annular metal portion 26.

The lower end of this latter cylindrical portion 24 is substantially closed by end member 21, there being, however, a central aperture 28 therein and surrounding this central aperture is an attachment element somewhat similar to a a snap fastener button as designated by the numeral 29 and this has an aperture 30aligned with the aperture 28 aforesaid. This permits detachable connection with the ear piece 30 The portion l5, embodying our present inwhich is shaped individually for each ear and serves to maintain the device in proper position with relation to the auditory canal of the ear.

Disposed within the larger cylindrical portion 24 is a thin steel diaphragm 3| which is in the form of a disc having a thickness of-approximately .001 inch. This may be made of any suitable steel providing the requisite properties such as stainless steel. soldered, brazed or otherwise secured to this diaphragm is the plate member 32 which responds to the pull of the magnets within the casing I6 and thus which sets up vibrations of the diaphragm 3| corresponding to the sound waves which the source propagates. This diaphragm is secured in place at or about the bottom of the cylindrical portion 22 by means of a ring or annulus 33 which passes over the threads 23 and firmly holds the diaphragm in position.

At or about the upper end of the smaller cylindrical portion 24 is another diaphragm which is water as we find that other liquids are also satisfactory. The major considerations in connection with the liquid between the diaphragms are" that (1) the liquid must be incompressible, (2) the liquid must have little or no volume change within the temperature range encountered between the coldest winter day and the hottest summer day, (3) the liquid must be unchangeable in its characteristics, i. e.,-stable, (4) the liquid must be non-corrosive, and -(5) the liquid must have the capacity to dampen sound waves and to limit the volume or intensity of the sound output of the device. We find that while water serves satisfactorily, distilled water being somewhat better than tap water, a small proportion of alcohol may be added to prevent freezing in cold weather and the proportions of water to alcohol are such that the mixture will not freeze at say 20 below zero. We may, however, use a mixture of about 50 per cent glycerin and about 50 per cent water or so-called hydraulic brake oil which we understand is composed of a mixture of castor oil and alcohol as well as other mixtures which meet the above conditions and the use of the word "liquid hereinafter is intended to include the The casing l6 of part H of the headphone or earphone l3 has a plug extension 31 to connect 'wires 38 as shown. Figure 1 shows also a typical circuit used in a hearing aid device. In assembling the part l5 either diaphragm is placed in position first and secured in place by' the securing means shown for ,that purpose. Then the space which subsequently forms the chamber when the other diaphragm is positioned is overfilled with the water or other liquid used and then the other diaphragm is positioned and secured in place, excess water being displaced by the act of positioning the second diaphragm and hence in this way complete filling of the chamber with liquid is insured while at the same time preventing any air pockets or air bubbles from being formed or trapped in the chamber. It will be understood that when the top diaphragm is placed in position first the part I5 is above defined therebetweenand in actual prac tice the diaphragm's are of such size and spacing that only a few drops of liquid are required to flllthe. chamber thereby produced. Of course changes in the liquid used in any given instance aifects' the dampening nature of our invention but we so select'that liquid as to produce little or no diminution of volume of sound waves having a frequency within the speech range while at the same time considerably dampening sound waves having frequencies above the speech range. Different liquids also enable somewhat modified results to be produced so as to adapt the invention to various conditions of impaired hearing. This cannot be done by present devices.

We find that our structure is such that the higher the frequency of the sound wave and the louder the noise the more it is dampened and hence metallic noises, noises from trailic or electrical equipment are very greatly diminished with consequent marked improvement in the quality and clarity or sound waves within the speech range. Frequencies below the speech range are also somewhat affected but these are ordinarily not suchas interfere with hearing whenusing a hearing aid device. Sharp or rasping noises are softened, however, regardless of their frequen y.

In actual practice'use of our modified hearing aid device has improved the capacity of those with impaired hearing to distinguish speech and conversational tones with marked facility. The utility oiv the device is broad, therefore, and whether the wearer isutilizing the same on the street, in a restaurant, or in any more or less noisy locality the results herein set forth are adequately accomplished.

The above is intended more as illustrative than as limitative and we may make certain variations, substitutions, additions or omissions without departing from the scope and principles of the invention. The various portions of the device which are associated with the ear may be made of any desired metallic or non-metallic material and of such size and configuration as will best suit circumstances of use. While we have shown .diaphregms of difierent size, this is not intended to constitute a limitation upon our invention because the use of diflerentiy sized diaphragms is more or less necessitated by space and size limitations in connection with a human ear. Our invention may, therefore, assume difierent specific forms and all such changes are deemed to be a part of the present invention and to be covered by the appended claims.

3 While specifically designed for hearing aid devices our invention is applicable to amplifying devices, speakers or'systems having similar or analogous uses or wherever the principles thereof find application. While we have set forth a preferred diaphragm thickness of .001 inch, we find.

that, depending upon conditions and the results to be produced, we may utilize a diaphragm having a thickness within the range of approximately .001 inch-.003-inch. In one particular case we have used a diaphragm .00150 inch in thickness with entire success. 7 While we prefer a steel diaphragm we intend to include within the scope of our invention diaphragms of other suitable materials whether metallic or non-metallic.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In a hearing aid device, an internally threaded cylindrical portion, a steel diaphragm approximately .001 inch thick disposed in said cylindrical portion, a central magnetic plate secured to said diaphragm, means for holding said diaphragm in proper position in said cylindrical portion, a second internally threaded cylindrical portion integral with said first cylindrical portion, a steel diaphragm approximately .001 inch thick disposed in said second cylindrical portion, means for maintaining the same in proper position therein and an incompressible vibration dampening liquid confined between said diap agms.

2. In a hearing aid device, a headphone comprising a casing having a threaded extension and a cylindrical portion which is internally threaded for engagement with the threaded extension of the casing. said casing being provided with a core having an electrical winding therearound and a magnetic element operatively associated with said core and winding and having spaced magnets symmetrically disposed with respect to said core, said cylindrical portion having a cylindrical extension integral therewith, a thin steel diaphragm in said cylindrical portion and a second thin steel diaphragm in said cylindrical extension, an incompressible liquid completely filling the space between said diaphragms, means to hold each diaphragm in place so that it is in effect supported only at its periphery, a plate member secured to of said diaphragms and means for transmitting air vibrations from said other diaphragm to the auditory canal of an ear in such manner that vibrations having a frequency in excess of 2048 vi rations per second are dampened.

JOHN B. NELSON.

WEILRRD C. MASON.

CERTIFICATE OF CORRECTION. Patent No. 2,266,788. Decerqbe'r 2'5, l9hl.

JOHN B. NELSON, ET AL of the above numbel ed patent requiring corr ectionas follows: Page 1, sec- 0nd column, line 51;, for "vibrstions" read variations-.; page 2, first column, line 29, for vibartions" read- -v1bra t1ons--; and that the .said Letters Patent should be read with this correction therein that the same may conform to the record of the ease in the Patent Office.

Signed and sealed this 17th day of February, A. D. 19 42 Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 2,266,788. Decenrber 33, 1914.1.

JOHN B. NELSON, ET AL,

ond column, line 51;, for "vibretions" read -variations-g page 2,'-first column, line 29, for vibartions" read- -vibrations; and that the said Letters Patent should be read with this correctie n therein that the seme may conform to the record of the ease in the Patent Office.

Signed and sealed this 17th day of February, A. D. 19 4.2

' Henry VanArs dal8, (Seal) Aciirig Commissioner of Patents. 

